Development of a Heat Transfer Model for Quenching by Submerging

Abstract

In quenching by submerging the piece is cooled due to vaporization, convective flow and interaction of both mechanisms. The dynamic of these phenomena is very complex and the corresponding heat fluxes that appear are strongly dependent on variables such as velocity of fluid and vapor fraction. This local dependence may produce very different cooling rates along the piece, responsible for inappropriate metallurgical transformations, variability of material properties and residual stresses.
In order to obtain an accurate description of cooling during quenching, a mathematical model of heat transfer was developed. The model is based on the mixture-model for multiphase flows, including an equation of conservation of energy for the liquid phase and specific boundary conditions that account for evaporation and presence of vapor phase on the surface.
The model was implemented on Comsol Multiphysics software. Generation of appropriate initial and boundary conditions, as well as numerical resolution details, is briefly discussed.
To test the model, simple flow conditions were analyzed. The effect of vapor fraction on heat transfer is assessed. The presence of the typical vapor blanket and its collapse can be recovered by the model, and their effect on the cooling rates of different parts of the piece is analyzed. Comparisons between numerical results and data from literature are made.